Radio testing device



-May 12, 1931. D, HAWLEY 1,805,089

RADIIO TESTING DEVICE -Fiied April 2s, 1926 z'sneets-sheet 1 fly! May12, 1931.A D. HAWLEYI RADIO TESTING DEVICE `Filed April 23, 1926 2Sheets-Sh'eret 2 r/MMM m JN @Niel mnu. @mw S @Q5 ,mwnmwh SNN n wm hx @N@Hmmm mw, one@ Nm um wm rwwjd) ,HQ SN H nu g @H E i i E Q im E ,n xi@ Qw I im g T2 g Sv Nd N m @if MM-. ii L?, i Y M w @f m uw H Q T; 2 E N A.j. "L 2 .2m 2 w E n A i. G ,ik IQI w\\ Aw w QN. m\ I w I.. I v. I. il mmm Q Patented May 12,- 1931 juive-[EDI5,1-,1f1-1g5l PATENTOFFICE DOUGLASSHAWLEY, OF MINNEAIOLIS, MINNESOTA., -ASSIGNOR TO JEWELL ELECTRICALINSTRUMENT COMPANY, OF CHICAGO, ILLINOIS, -A CORPORATION OF. ILLINOISRADIO TESTING DEVICE 1 Appncation mea Api-11 23,

the filament voltage with the tube in operation, and the tube emissionwith the tube in operation. Moreover, it will test tubes foremissionunder varying grid biases; it

will test the condition of the A, B, C or D batteries as to theirpolarity, voltage or amperage; it will determine 'if the tube elementsare shorted internally and, if so, what elements are so effected; itvwill testlv resistance and condition of the phones, of the loud speaker,or the transformer; it will compare the resistance in one set with thatof another. l

In.. the accompanying drawings, the improved testing device isdiagrammatically illustrated, and I have'also illustrateddiagrammaticall -a radio receiving set of a well known simple type.

Referring to the drawings:

Fig. 1 is a diagrammatic view ofthe radio receivingnset; and 0 Fi is adiagrammatic view of the test- 1ng evice.

'Of the' parts of the radio receiving set diagrammatically illustratedin Fig. 1, it is ments, to wit: vA batter Y filament contacts F and F,ofl which F may desirable for the purposes of this case to particularlynote only the following ele- A, B battery B, C` battery C, loud spea rer3, grid leak and condenser 4, antenna. coupler 5, radio frequencytransformer` 6, audio frequency transformer 7, and sockets 8, 9 and 10.Thesesockets have,the customary contacts, to wit: the grid contacts G,plate contacts P, and

be assumed tovbe vthe negative contact.

1 The testing apparatus, as its chief elements v192e. serial No.104,044.

Aincludes abattery 11, a socket 12, a meter 13",

preferably a` combined voltameter and a milliammeter, and a plug'll,said parts being associated with ,circuit-s, switches and cooperatingdevices, as will now be described.,

In this particular'instance,'the battery 11 may be assumed to be' a fourand one-half volt source. The socket 12 is 'or may be assumed to be aduplicate of one of the sockets 8, 9, or 10 illustrated diagrammaticallyin Fig. l and, consequently, the socket contacts are correspondinglymarked. The plug 14 has four contacts g, p, f. and f3. This plug -14: isof the same slze as the base of a radio tube and its contacts arecorrespondinglyv arranged, so that it will fit in any one of the socketsas a substitute for the tube, thereby bringing the circuits of the setto the testing device. lMain -lead wires or bus bars g', p', f and f2lead, respectively, from the plug contacts g, p, 7 and f3. The leads fand f2v are connected directly to thev contacts F and F of the socket12. Main leads or bus bars 15 and 16v lead, respectively, from the meter13, the' lead 15 being the common negative and the lead 16 being-amilliammeter lead. The numerals 17 and 18 indicate, respectively, lowvoltage'and high voltage leads or bus bars that extend from the meter13. The lead 18 also serves asa low reading milliam'- meter lead. Mainleads or bus bars 19 and 20 extend, respectivel from the negative andpositive sides o the battery., Mam leads or bus bars 21 and 22 extend,respectively, from the contacts G and P of the socket 12.

The several switches for making the varicontacts connected,respectively, to the bu's bars 20, 17, 21 and 15. The fourthgroup 26 iand The fifth group 27 consists of four contacts connected,respectively, to the bus bars 177,18, 1,5 andjg; The sixth group 28`.consistant eight normally separated contacts'connected,respectively, tothe bus bars -f `19, 21,520, 16,22 and 15. The seventh group 29 consistsof eight normallysepa'- ratedl contactsI connected, respectively,` tothe bus bars f', 20, 21,19, p,16, 22 and 15. The eighth group 30consists of six normally separated contactsv connected, respectively, tothe bus bars 21, g', p', 16, 22 and 15. The ninth group 31consists offive normally separated contacts connected, respectively, to the busbars f', 17, 21, g and l5. The tenth group 32 consists of ve contacts,connected, respectively, to the bus bars f2, 17 21, g! and 15. Theeleventh group 33 consists of four contacts connected, respectively,

' to the bus bars f2, 17, f and 15. `The twelfth group 34 consists offour contacts connected, respectively, to the bus bars f', 17 ff? and15. The thirteenth 'group 35. consists o five contacts connected,respectively, to thebus bars 22, p', 18, f2 and/15. Y

As shown and preferred, the bus bars 16, 18, 20,` 19, 17 and 15 areextended to and terminate in contacts ofthe character usually designed`as tip jacks, indicated by the same numbers as the bus bars themselves,but with the exponent a added.

The triangular :black ymarks onFig. 2 are intended to v indicate lwedgesof insulating material operative on the several groups -ot switchcontacts, the wedges for the several switches being indicated by thesame characters with the added exponent a. In some of the groups,insulating material is placed between certain of the contacts so thatthe said contacts are arranged to operate in pairs.

The switch 23 is for making tests for gridplate shorts; the switch 24 isfor making tests for plate-filament shorts; the switch 25 is' for makingtests for grid-filament shorts; the switch 26 is for making tests forcontinuity; the switch 27 is for testing for grid leak and condenser;the switch 28 is forl testing emission ofthe tube with -negative gridbias; the switch 29 is for testing for emission of the tube withpositive grid bias; the switch 30 is for testing for emission of thetube as used in the set; the switch 31 is for testing the grid bias atthe socket; the switch' 32 is for making the same test as the switch 31,but with` the filament connection reversed; the switch 33 is vfor makingtest for the filament voltage; the switch 34 is for maln'ngthe same testas the switch- Y 33,but with the meter connections reversed;

l' voltage.

and the switch 35 is :for testing the plate For the first four testscontrolled by the switches 23, 24, 25 and 26, it is. not necessary tohave to insert the plug 14 in either of the sockets 8, 9 or 10 of thereceiving set, but

for the tests controlled by the switches 28,

29 and 30, the tube to be tested will be inserted in the socket 12 ofthe testing device.

For other tests, that is, for testing the condition of the set,f`theplug 14 must be in serted inone or theffother of the sockets 8, 9

`orv 10. v

When'l the switch 23 is operated by thewedge 23a, the bus bar1'9w1ll beconnected to the bus bar 21 and the bus bar 15 will be connected to thebus bar 22; and if a volta-l .it will indicate thatthe plate is shortedto the filament.

' When the switch 25 is operated by the wedge 25a, the bus bar 20 willbe connected to the bus bar 17 and the bus bar 21 will be connected tothe bus bar 15; and if the meter 13 then shows a reading, it willindicatev that the grid and the filament are shorted.

When the switch 26 is to be o erated,

the tip jacks 17a and 20a should e connected by a circuit whosecontinuity is to be tested, and then when the wedge 26a is pressed, thebus bars 19 and 22 will be connected and 'if the meter 13 shows areading,

it will indicate that the circuit being tested 'is continuous.

In tests made by the switches 27 to 35,.

inclusive, the plug 14 will be inserted in one or the other of thesockets 8, 9 or 10 of the receiving set. In making the test by theswitch 27, theplug 14 must be in the socket 9, but in making the othertests, the plug lnay be in the one or the other of the sockets 8, 9 or10, depending upon which circuits are to be tested. When the wedge 27 ispressed, the bus bar 18 will be connected to the bus bar 'p' and the busbar 15 will be connectedl to the bus bar g', and then-if the meter 13shows the proper l. -reading,git will indicate that both the grid busbar 19, the bus bar `21 will be connected to thebus bar 20, the bus barp will be connected to the bus bar 16, and the bus bar 22 will beconnected to the bus bar 15;

and the reading o f the meter. will then show the emission inmlliamperes of the tube` with a negative bias.

When the wedge 29* is ressed, the contacts of the switch 29 wi beengaged so that the bus bar f will be connected to the bus bar 20, thebus bar 21 will be'connected to the'bus bar 19, the bus bar p will beconnected to the bus bar 16, and the bus bar 22 will be connected to thebus bar 15; and the reading of the meter 13 will then show the emissionof the tube in lmilliamperes with a positive bias.

When the wedge 30 is pressed, the contacts of the switch 30 willbeengaged .so that the bus bar 21, will be connected to the bus bar g',the busybar p will be connected to the bus bar 16, "and the bus bar 22rwill be connected to the bus bar 15; andthe reading on the meter 13will show the emission of the tube as in actual use in the set. 1 v

When the wedge 31 lis ressed, the contacts. of the switch 31 wil beengaged so that the bus bar f willbe connected to the bus bar 17 and thebus bar 21 vwill be connected to the b us bars Vg and :15; andthereading on the meter 13` will then lshow the bias voltage at.;the;;,socket when the grid return is to f',

When the wedge"`ii`*32?L 'is ressed, the contacts of theswitch 32 wil beengaged so that the bus bar f2 will be connected to the bus bar 17 andthe bus bar 21 will be connected to thebus' bars g andf15; and thereading on the meter 13 will then show the bias voltage at the socketwhen the grid return is to f2;

When the wedge`33=I is pressed, the con-- tacts of the switch'33'will beengaged so that the bus bar f2 will be connected to the bus bar 17 andthe-bus bar f will be con-v nected to the bus bar 15; andthe meter 13will then give the lament'vvoltage reading.

When the wedge-34a. isfpressed, the contact switch 34 will be engaged sothat the bus bar f will ybel connected to the bus bar 17 and the bus barf2 vwill be connected to the bus bar 15; and the meter 13 will'then showthe filament voltage reading. The switch 33 or 34 will lbe usedaccording to the connection of. the A battery to the socket. l

When the wedge 358L is pressed, the contacts of the switch 35 will beengaged so that the bus bar 22 will be connected to the bus bars p and18, and the bus bar f2. will be connected to the bus bar 15;` and` thereading on the meter 13v will then show the. plate voltage at thesocket. I

In the drawin s only meter 13 is used for the several differentpurposes, but, of course, more than one meter mi ht be coupled and theseveral meters used or different tests or indications. l e e The numberof groups of switch contacts may be varied according to the number ofdifferent tests that it may be -desired to make and, of course, anysuitable switchseveral circuits of the receiving set, it has beennecessary to have the batteries of the set connected in the respectivecircuits.

What I claim is: `1. A testing device ofthe kind described comprising aplugadapted to be inserted into a socket of'an electron tube circuit and-having contacts corresponding to those of the removed tube, thecontacts of said plug having leads corresponding to the socket contacts,an indicating meter having leads, a socket forming part ofthe testingapparatus and having connection with the leads extended therefrom, and ay plurality of switches, each switch involving a plurality (of. contactsand the contacts of said switches having leads, certain of which areconnected to'` the several leads above noted, certain of the lswitchcontacts and their leads beiner arranged for testinr of the conditionof5 the several circuits of the electron tube circuit and certainthereof being arranged for testing the condition of a tube inserted inthe socket of said testing device, the condition of the tested circuitsand the tube to be tested being indicated on said meter. 4

2. A'testing device of the kind described comprising a plug adapted tobe inserted into a socket o an electron tube circuit and having contactscorresponding to those of the removed tube, the contacts of said plughaving each its own lead, an indicating meter having a plurality ofindependent leads and a plurality of independent switches, eachinvolving a plurality of contacts, said contacts having leads differen-rtially connected to the several leads enumerL ated, one switch beingarranged to test the grid bias, another to determine the c ondition ofthe grid leak and' condenser, another of said switches being arranged totest the filament voltage, another of said switches to test the plateVoltage, and a means in connection with said testing device for enablingcertain tests tobe made under conditions -that would exist inthe circuitbeing tested if a tubewas not removed therefrom.-

43. A testing device of the kind described comprising a plug adapted tobe inserted into a socket of an electron'tube. circuit and having'contacts corresponding to thoseof the removed tube', the contacts -ofsaid plug having each its. own lead, a socket having contactscorresponding tol those of a` tube socketin the circuit to be tested andadapted totl receive the contacts of a` tube removed from the circuit tobe tested, s aid socket contacts having leads, an indicatlng meterhavving bus bar leads, and switches, each involvto test for emission ofthe tube, the said` socket in the testing apparatus enabling a tuberemoved from the circuit being tested to be inserted therein and coupledback into the circuit being tested thereby permitting tests to be madewith respect to conditions Y that prevail in the'circuit under`operating conditions thereof.

4. A testing apparatus for electron tube circuits 4including a localtesting circuit adapted for use with a remote circuit tobe tested and asource of potential, an indicating meter, a plurality of connections,means connecting said connections with said remote circuit to be tested,a plurality of independent switches for alternately estabv lishingconnection between said remote circuit to be tested, said indicatingmeter, and` said local testing circuit, said remote circuit to be testedincluding the circuit connections of an electron tube system, and saidlocal testing circuit further including the -elements of an electrontube adapted for use in `the circuit being tested whereby the conditionsprevailing in the circuits of said electron tube system, under operatingconditions thereof, maybe determined.

5. A testlng device including leads connectable to certain of the tubeelement leads in an electron tube circuit to be testedwhen 1 a tube isremoved therefrom, means connectable to certain of said leads forproduclng a load or drain eifect on the circuit to be tested equal tothat of a tube removed therefrom, and indicating meter means convnectable to certain of said leads, therebypermitting the measurement ofvoltage and current flow that would exist in the circuit of a removedtube if the removed tube were in operating position in the circuit.

6. A testing apparatus for use with an electron tube circuit to betested including .a plug havf'ing contacts corresponding to those of atube in av circuit to be tested and .connectable to the'circuit contactsof a tube socket in the circuit to' be tested when a tube is removedtherefrom, a socket-.having contacts corresponding to 'those' of asocket in the circuit to be tested and adapted to receive the contactsof a tube removed from the circuit to .be tested, leads arranged toconnect the contacts of the plug with the` contacts of thesocket 'thetesting' alpparatus whereby when'the contacts of t e tube equal tothat-of atube,A removed from the socket ofa circuit toV beLtested-isplaced in the socket in the testing apparatus, a

`drainor'load effect on the circuit being tested will be produced thatis equal to the drain or load effectv thereon when the removed tubeisinthe socket of the circuit being tested, and electrical measuring meansarranged for connection to said leads thereby permitting the measurementof voltages and current How at the socket of the circuit to be testedthat would exist 'under' operating conditions.

7. A`v testing device for use with a remote circuit'to be testedincluding a means for producinv the drain or load-effect, on a circuit,o? a tube in the circuit 't0 be tested, leads from said means arrangedfor connection to the remote circuit to be tested when a tube is removedtherefrom, electrical measuring means arranged for connection withcertain of said leads thereby permitting the measurement of voltages and`current flow in the circuit being tested equalto the voltage andcurrent iiow existing therein when` the removed tube is in its place.

8. A testing device for testing remote electron tube circuits including'a plug having contactsy corresponding to those of an electron tube inthe circuit to be tested and coupled to the circuit vcontacts of a tubesocket in the circuit to be tested when a tube is removed therefrom, asocket in the testing device having contacts corresponding to those of asocket in the circuit to be tested and adapted to receive`a tube removedfrom the circuit to be tested, leads for establishing contact betweenthe lug contacts and the contacts fof thev socEet in the testingapparatus whereby, when a plug is inserted into the socket of aremovedtube in the circuit to be tested, and elements equal to those of theremoved tube are connected to the corresponding contacts of a socket inthe testing apparatus, drain or load ei'ect' on .the circuit beingtested will be produced that is equal to the drain or load effectthereon under operating conditions, electrical measuring means, andswitch means for alternately connecting said measuring means between theplate and a filament lead for testing the las vacuum tube socket and anelectrical indieating instrument mo'unted thereon, a con-v tact plugseparate from said support, and connections between .said plug, socketand indicating instrument, said plug being adapted to engage thecontacts of a vacuum tube socket of a radio set.

10. A testing device of the character set forth comprising a support'having a vacuum tube socket,.vo1tmeter and a milliammeter mountedthereon, a contact vplug adapted to engage -the contacts of a vacuumtube socket of a radio set, flexible leads connecting said plug withsaid support, circuits including said leads, first mentioned socket,voltmeter and millianii'neter, means for connecting the meters in saidcircuit to indicated voltage or milliamperes between predeterminedcontacts of the.' first mentioned socket.

11.In atesting device for audion circuits, the combination of aconnector meinthe socket, conductors leading from saidber adapted to beconnected to.- an audion tube socket and having a plurality of con'-tacts for engagement with the contacts of v connector contacts, and anelectrical measuring instrument connected to ypredetermined conductorsand adapted to determine the voltage conditions existing at thecorresponding predetermined contacts of said audion tube socket.

12. In a testing device for audion circuits, the combination of anelectrical connector adapted to -be engaged with an audion tube socketand having contacts corresponding to the filament and plate termi? nalsof an audion tube, leads from said conacts, an electrical measuringinstrument asociated with said connector, and selective switching meansfor connecting said ineasuring instrumentto measure open circuit socketfilament voltage or open' circuit socket."

plate voltage.--

13. In a test1 adapted to be engaged with an audion tube socket andhaving contacts corresponding to the filament and grid terminals of anauf dion tube, leads. from said contacts, an electrical measuringinstrument associated with said connector, and selective switching meansfor connecting said measuring instrument to measure open circuit socketfilament `voltageH or open circuit socket grid voltage.

ng' device for audion circuits, the combination of an electricalconnector the grid, plate and filament terminals of an audion tube,leads from said contacts, electrical measuring means associated withsaid connector., and selective switching means for connecting saidmeasuring instrument to vmeasure open circuit socket filament voltage,

open circuit socketplate voltage or open circuit socket grid voltage.

. 16. The method of testing audion tube circuits wth a testing devicehaving a test connector, meter and socket contacts which comprisesconnecting the test connector of the testing device to a socket of theaudionv ftube circuit, placing` an electron tube in the socket-@of thetestingjdevice,operating the circuit, .and determiningv the electricalcon-- ditionv of the circuitaunder predetermined currentflow'conditions. f

17 .i The method of testing receivingsets employing audiont'ubesjwith atester having 85 a test'connector,` socket and meter, which comprisesvremoving an lelectron, tube from.

' the set, substitutingthetest connector of the testing device, placingan electron tube in the socket of the testing device, operatingthereceiving set with the tube in the testing device, and measuringpredetermined electrical conditions in the receiving set underoperation.

18. AThe method of testing receiving setsy employing audion tubes with atester having a test connector, socket and meter, whichcomprisesremoving an electron tube' from vthe set, substituting the testconnector of the testing device, placing an electron tube correspondingto the removed tube in the socketof the testing device, operating therecelvin set with the tube in the testing device, an :measuringpredetermined electrical cond1.y fi tions in the receiving set under.opera-tion.

19.- In a testing device for audion circuits, the combination oft aconnector member adapted to'be connected to an audion tube socket andhaving a plurality of. contacts for.

engagement with the contacts of the socket,f.110

conductors leading from said connector contacts, means for producing acurrent ilow equivalent to an operating condition in one of said. audioncircuits, and an electrical meauring instrument adaptedV to determinethe electrical conditions in the circuits under such operation. .j l

20. In a testing device for audion circuits, the combination of aconnector member adapted to be connected to an' audion tube 120 socketand having a plurality of contacts for engagement with the contacts ofthe socket, conductors leading from said connector` contacts, means forproducing a current.' iow, voltage and current 'measuring means .125

J for determining voltage conditions existing at certain contacts ofsaid audion tube socket, and fordetermining current vflow betweenpredetermined of said contacts, and selective switch means forconnecting said measuring means between predetermined contacts,

21. In a testing device for audion circuits,

.the combination of an electrical connector adapted'to be engaged withan audion tube `socket and having contacts corresponding to terminals ofan audion tube, leads from said contacts, an auxiliary audion tubesocket associated -ivith said connector, an

electric measuring instrument associated with said connector, andselective switching means for connecting said 'measuring instrument tomeasure filament voltage with the audion circuit under load operation.

22. In a testing device for audion circuits,y tlie combination of anelectrical connector .adapted to be engaged with an audion tube socketVand having contacts corresponding to terminals of' an audion tube, leadsfrom said contacts, an auxiliary audion tube socket associated vwithsaid connector, an electric measuring instrument associated with saidconnector,'and selective switching means for connecting said measuringinstrument to measure grid voltage under load.

23. In a testing device for audion circuits, the combination of anelectrical connector adaptedl to be engaged with an audion tube socketand having contacts corresponding to terminals of an audion tube, leads-from said contacts, an auxiliary audion tube socket associated withsaid connector, an' electric measuring instrument associated.`

with said connector, and selective switching means for connectingvsaidmeasuring instru-- fment to measure plate voltage under load.

24. In a testing device for audion circuits, the combination oanLelectrical connector adapted to be engaged with an audion tube socketand having contacts. corresponding 'to terminals of an audion tube,-leads from.

said contacts, an auxiliary audion tube socket associated with saidconnector, an

electric measuring instrument associated with said connector, andselective switching means for connecting said measuring instrument tomeasure plate voltage, grid voltage or filament voltage under load.

25. In a testing'4 device for electron tube circuits, the combination ofelectrical measuring means for determiningvoltage and current conditionsin the audion circuit,

4with a socket for receiving an audion tube',

current conditions in the audioncircuit, with a socket for receiving anaudion tube, conductor means extending from said socket, v

connection means having contacts corresponding to vthe terminals of anaudion tube for connecting the device to the audion socket of the audioncircuit whereby the audion circuits may be tested with the audion inoperation iii the circuits, and auxiliary connectors and leads to saidelectrical measuring means whereby the measuring means may be connectedto external circuits.

27. In a testing device for electron tubev circuits, the combination ofelectrical measuring means for determinng voltage and current conditionsin the audion circuit, with a socket for receivin van" audion tube,conductor means exten ing from said socket, connection means vhavingcontacts corresponding to terminals of an audion tube'for connecting thedevice to the audion socket of` the audion circuit whereby the audioncircuits may be tested with the audion in operation in the circuits,auxiliary binding posts and leads to said electrical measuring meanswhereby the measurin means may be connected -to'externalcircui s, andselective switch. means for controlling'tlie'dconnection of saidmeasuring vmeans to said audion circuits..

28. In a testing instrument for audion tube circuits, the combination ofa connector adapted to be engaged with anaudion tube socket,` conductorsleading from said con- Jnector, an socket for receiving'- the audiontube, meter means having a high? voltageand a'low voltage range, switchmeans for connecting said high voltage meter means across the platecircuit or'said low voltage meter' vmeans across the filament circuit,-a low voltage battery carried by said testing instru- "ment, and switchmeans for controlling the connection of saidbattery in series with saidlow voltage meter means.

29. In a testing instrument for detecting electrode short circuits inaudion tubes, the combination of an audion tube socket, with a vacuumtube of the audion type, a low voltage battery and an electric meteradapted to indicate short circuit of said battery, circuits'extendingfrom the socket'contacts, and selective switch means for connectingpredetermined electrodes in series with said battery and meter to shortcircuit the battery through contacts corresponding to predeterminedelectrodes and determine the presence of electrode short circuits.

v30. In a testing instrument for detecting electrode short circuits inaudion tubes, the combination of an audion tube socket, with a vacuumtube of the audion type', a low` voltage battery andan electric meteradapted 'to indicate short circuit of said battery,

lcircuitsifrom the contacts of the socket and selective switch means forconnecting the ica iio

plate and filament, the plate and grid or the and Vfilamentrespectively, in serieswith to those of a tube wlth conductors leadingfrom certain contacts of said test connector,

an auxiliary socket for receiving the tube to be energized from 'saidsocket, a standard source of electromotive force carried by said beinserted yin the socket tester for impressing an additional increment ofelectromotive lforce von the grid, and an electrical measuringinstrument for determining the plate current under such condition. l

32. In a device of the class described, the combination of a testconnector adapted to of an electron tube circuit and having contactscorresponding to those of a tube with conductors leading leads from saidcontacts,

from certain contacts of said test connector, an auxiliary socket forreceiving the tube to be energized from said socket, a standard sourceof electromotive force carried by said tester for impressing anadditional increment of electromotive force on the grid, an electricalmeasuring instrument for determining the plate current under suchcondition, auxiliary binding posts flor said stanelectrical measuringinstruments associated with said connector, and selective switchingdevices for connecting said measuring instruments to measure platecurrent or lament voltage under load.

36. In a testing device for audion circuits, the .combination of anelectrical connector adapted to be engaged With an audion tube socketand having contact terminals, flexible leads from said contacts, anaudion tube socket, a plurality of electrical measuring instrumentsassociated with said leads, and selective switching devices forconnecting said measuringinstruments to measure plate current or platevoltage at said latter socket under load.

37. In a testing device for audion circuits, the combination of anelectrical connector adapted to engage contacts of an audion tubesocket, wi-th flexible leads from said contacts, an auxiliary socketenergized by dard source, and selective switch means for i disconnectingsaid source from said conductors and connecting said measuringinstrumentl with said binding posts for continuity tests. p f

33. In a testing device for audion circuits, the combination of anelectrical Iconnector adapted to be engaged with an audion tube socketand having contacts corresponding to plate and grid contacts of. a tube,leads from said contacts, an electric indicating device, and means forconnecting said device across the plate and grid terminals of said testconnector to indicate the condition of a grid leak.

34. In a testing device for audion. circuits, the combinationvof anelectrical connector adapted to be engaged with an audion tube socketand having contacts corresponding to grid and plate terminals of a tube,leads from said contacts, an auxiliary audion tube socket associatedwith said connector, an electrical measuring instrument associated withsaid connector, and means for connecting said measuring instrumentacross the grid and plate contacts of said connector to measure theresulting current and determine the condition of a grid leak andcondenser. v

35. In a testing device for audion circuits, the combination of anelectrical connector adapted to be engaged with an audion tube socketand having contact terminals, fiexible an audion tube socket connectedto said leads, a plurality of

